Score : $100$ points
Takahashi wants to print a document with $N$ pages double-sided, where two pages of data can be printed on one sheet of paper.
At least how many sheets of paper does he need?
Input is given from Standard Input in the following format:
Print the answer.
By printing the $1$-st, $2$-nd pages on the $1$-st sheet, $3$-rd and $4$-th pages on the $2$-nd sheet, and $5$-th page on the $3$-rd sheet, we can print all the data on $3$ sheets of paper.